"We're in a large cave, all right," observed Joe, casting eager eyes about. "There's another opening away over there," pointing to the far side of the cave. "Let's go through it and see where it leads us." The hole was so small that the boys barely got through crawling on their stomachs. But at last they reached the other side, and Bob turned the light ahead. "Just another cave," said Bob. "Chances are----" "Wait!" started Joe, gazing at the darkness before them. "Let's have some light over there." The beam was turned in the direction indicated by Joe, and the next moment the boys gave startled exclamations. "A narrow passageway," observed Bob. "Come on. We'll see where it takes us." Suddenly, as they rounded a sharp corner, the youths came face to face with something that made them cry out in delight. There, directly before them, was a large underground pool of sparkling water. With a word of thanksgiving the young men rushed over and gulped up large quantities of the precious fluid. "At last!" cried Bob, too happy for words. "At last we've found water!" CHAPTER XXI Captured! To the two boys, who had hoped against hope that their parched throats could be relieved, the priceless water tasted like nectar. They had felt sure that grim tragedy was near. Now their spirits were restored to a new high level, and they considered themselves equal to anything. At last, when they had fully quenched their thirst, they glanced about the cavern. Near the edge of the pool were the tracks of wild animals, which had evidently made this place a frequent haunt. The youths did not recognize all the imprints, but Joe stoutly declared that gazelles had been there. "Doesn't seem pleasant to know that we've been drinking after wild animals, does it?" laughed Bob. "No. But we won't think of that, especially since our thirst was so great. Then, too, it's not likely that many germs are to be found away out here in the desert mountains." The youths stretched out on the cool white sand beside the pool. The atmosphere in the cavern was such a departure from the fierce outside heat that they were content idly to while the time away, despite the fact that they should be getting back to camp. At times they bent over to drink of the refreshing water, delightfully knowing that they could have all they wanted. Then they grew drowsy and gradually fell asleep, a thing that they should not have done. At last they were awakened--suddenly! Every nerve in their bodies seemed tense. Something told them not to move. Slowly they edged around and looked toward the back of the cave. Then they started, as a savage growl rent the air. A fierce tiger cat was crouched ready to spring. It had evidently come to the pool for water when it had discovered the youths. There was no time to take aim with their rifles, for the beast would be upon them. Slowly Bob reached for his pistol, and Joe followed suit. At last the boys were ready for action.